Skin to Ski: Double Rip
After the final ascent, the change from skinning to skiing is unique. Instead of two single-skin rips, it's much faster to double-rip both skins and stuff the sticky mess in your suit.
Doing a double rip in less than 10 seconds is possible with enough practice with the right gear. Think of 20 seconds as a maximum.
Note that the first ten steps of the double-rip are the same as a single rip. See below or more info on when the double-rip varies.
The following method is one of many. Different body mechanics and levels of flexibility may require some adjustments. Practice it a lot, and then make it your own.
Entering a transition zone is similar for every type. Review the entrance process as part of practicing each transition type.

When your boots lock, your hands will be close to your bindings. Take advantage of their proximity. Reach back to open the heel piece of the left-hand binding. At the same time, extend your right arm for balance.
But don't try and open both bindings at once. That makes you crouch on two tip-toes which is unstable. Falling over wastes time.
Unlike a single-rip transition, do not stand up and do not fold the first skin. Stay low and...

Slide the left ski forward as your left arm pulls backward. Sliding the ski forward will help remove the whole skin without having the tail stick and get caught under the ski.
As you rip the left skin, stay bent over and balanced on your right toe.
Do not stand up.

With both skins in one hand, pull open your suit with the other hand. Stuff both skins deep into your suit pocket so that they clear the zipper.
You won't need to use your skins again, so you won't have to untangle the sticky mess until after the race.
Exiting a transition zone is similar for every type. Review the exit process as part of practicing each transition.
The following video breaks down the Double Rip skimo transition according to the above instructions.
The Skin to Ski skimo transition with double skin rips